Cooling Fan With One-Way Clutch Bearing

ABSTRACT

A cooling fan assembly, and method of operation, for use in an engine compartment of a vehicle is disclosed. The cooling fan assembly includes an electric motor having a motor shaft extending therefrom, a one-way clutch bearing mounted on and rotating with the motor shaft, and a cooling fan. The cooling fan includes a central hub with fan blades extending from the central hub. The central hub engages the one-way clutch bearing such that torque is transmitted from the motor shaft to the central hub in a first direction of rotation and torque is not transmitted from the motor shaft to the central hub in an opposed direction of rotation.

BACKGROUND OF INVENTION

The present invention relates generally to engine cooling fans and moreparticularly to engine cooling fans having a one-way clutch bearing.

Engine cooling fans are common in the engine compartments of automotivevehicles. Some engine cooling fans are now driven by electric motorsrather than mechanically driven off of the engine. These engine coolingfans have torsional resonance that can be excited on start-up, shutdown, or steady state fan operation by the axial or torsional cogging ofthe electric motors used to drive them. This may occur at multiple RPMlevels of fan blade rotational speed. This resonance may createobjectionable noise inside the passenger compartment over a broad rangeof the fan start-up or shut-down process. The concern is particularlypronounced for engine cooling fans having a diameter of forty-fivecentimeters and larger because the torsional resonance for theserelatively larger fans tends to have a higher amplitude. Some haveattempted to overcome this concern by modifying the cooling fan hub, butthis may compromise the strength of the fan. Also, material may beremoved to reduce the torsional stiffness of the blades, but this maycompromise the structure of the blades.

SUMMARY OF INVENTION

An embodiment contemplates a cooling fan assembly for use in an enginecompartment of a vehicle including an electric motor having a motorshaft extending therefrom, a one-way clutch bearing mounted on androtating with the motor shaft, and a cooling fan. The cooling fanincludes a central hub with fan blades extending from the central hub.The central hub engages the one-way clutch bearing such that torque istransmitted from the motor shaft to the central hub in a first directionof rotation and torque is not transmitted from the motor shaft to thecentral hub in an opposed direction of rotation.

An embodiment contemplates a method of providing torque from an electricmotor to a cooling fan in an engine compartment of a vehicle, the methodcomprising the steps of: activating the electric motor with an electriccurrent to provide torque to a motor shaft in a first rotationaldirection; providing torque in the first rotational direction from themotor shaft, through a one-way clutch bearing, to the cooling fan tocause rotation of the cooling fan in the first rotational direction; andpreventing torque from being transmitted in an opposed rotationaldirection from the motor shaft, through the one-way clutch bearing, tothe cooling fan.

An advantage of an embodiment is that the electric motor torsional inputoscillations are decoupled from the torsional mode of the cooling fan,which results in a reduction of start-up and shut-down noise that wouldotherwise occur due to motor windings exciting the torsional resonanceof the cooling fan. This also assures that the structural integrity ofthe cooling fan is not compromised.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a schematic view of a portion of an automotive vehicle.

FIG. 2 is an elevation view of a cooling fan assembly.

DETAILED DESCRIPTION

Referring to FIG. 1, a portion of a vehicle, indicated generally at 20,is shown. The vehicle 20 includes a passenger compartment 22 and anengine compartment 24. A power unit 26, such as an internal combustionengine, is mounted in the engine compartment 24. A condenser, radiator,fan module (commonly called CRFM) 28 may be mounted in front of thepower unit 26. The CRFM 28 may include one or more heat exchangers 30,such as a radiator and/or a condenser, as well as a cooling fan assembly32. An electric motor 34 in the engine compartment 24 includes a motorshaft 36 extending therefrom that engages and drives the cooling fanassembly 32.

FIG. 2 shows the cooling fan assembly 32 in more detail. The cooling fanassembly 32 includes a cooling fan 37 having a fan hub 38 from which fanblades 40 radially extend. The radially outer edges of the fan blades 40are supported by a fan outer ring 42. Mounted within the fan hub 38 is aone-way clutch bearing 44. The one-way clutch bearing 44 is also mountedon the motor shaft 36. The one-way clutch bearing 44 may be pressed intothe fan hub 38 or otherwise secure to the hub 38 to assure that an outerrace 46 of the one-way clutch bearing 44 will be fixed to (i.e., notrotate or translate relative to) the hub 38. The one-way clutch bearing44 may be press fit on the motor shaft 36 or otherwise secured to themotor shaft 36 to assure that an inner race 48 of the one-way clutchbearing 44 will be fixed to the motor shaft 36. The particularconfiguration of the one-way clutch bearing 44 may be one of severaltypes of one-way clutch bearings known to those skilled in the art. Withthis connection of the cooling fan 37 to the motor shaft 36, theelectric motor 34 can only transmit torque to the cooling fan 37 in onerotational direction.

The operation of the cooling fan assembly 32 and electric motor 34 willnow be discussed. When cooling fan operation is needed, the electricmotor 34 is activated. The motor 34 drives the motor shaft 36, which inturn provides a driving torque to the one-way clutch bearing 44. Thebearing 44 allows torque in the direction of motor rotation to betransmitted to the cooling fan 37 while preventing torque in theopposite direction to be transmitted. Thus, the motor 34 can drive thefan 37 even though the torque output of the electric motor 34 ispartially decoupled from the cooling fan 37. This results in adecoupling of the input forcing function of the cogging of the motor 34from the torsional resonance of the cooling fan 37. The end result,then, is that the amplitude of the torsional resonance of the coolingfan 37 is reduced, which results in reduced noise transmitted to thepassenger compartment 22.

While certain embodiments of the present invention have been describedin detail, those familiar with the art to which this invention relateswill recognize various alternative designs and embodiments forpracticing the invention as defined by the following claims.

1. A cooling fan assembly for use in an engine compartment of a vehiclecomprising: an electric motor having a motor shaft extending therefrom;a one-way clutch bearing mounted on and rotatable with the motor shaft;and a cooling fan including a central hub and a plurality of fan bladesextending from the central hub, the central hub operatively engaging theone-way clutch bearing such that torque is transmitted from the motorshaft to the central hub in a first direction of rotation and torque isnot transmitted from the motor shaft to the central hub in an opposeddirection of rotation.
 2. The cooling fan assembly of claim 1 whereinthe one-way clutch bearing includes an outer race that is press fit intothe central hub.
 3. The cooling fan assembly of claim 2 wherein theone-way clutch bearing includes an inner race that is press fit onto themotor shaft.
 4. The cooling fan assembly of claim 1 wherein the one-wayclutch bearing includes an inner race that is press fit onto the motorshaft.
 5. The cooling fan assembly of claim 1 wherein the cooling fanincludes an outer ring connected to radially outer ends of the pluralityof fan blades.
 6. A method of providing torque from an electric motor toa cooling fan in an engine compartment of a vehicle, the methodcomprising the steps of: activating the electric motor with an electriccurrent to provide torque to a motor shaft in a first rotationaldirection; providing torque in the first rotational direction from themotor shaft, through a one-way clutch bearing, to the cooling fan tocause rotation of the cooling fan in the first rotational direction; andpreventing torque from being transmitted in an opposed rotationaldirection from the motor shaft, through the one-way clutch bearing, tothe cooling fan.